1. The Field of the Invention
The present invention relates to products used in connection with practicing sports and more particularly to an enclosure within which a user may practice with a ball or similar object.
2. The Relevant Technology
Typical projectile barriers are made of netting or wire fencing mounted or secured to a pole frame. The netting or fencing surrounds user or player so a moving object (e.g., baseball, softball, soccer ball, golf ball, puck) will be constrained in a predetermined area.
Many practice cages are erected outdoors. Thus the cage is exposed to the elements including wind. Even though the projectile barriers (e.g., netting or fencing) have holes, they can be a barrier to wind. Thus the frame must be sufficiently rigid to support the netting or fencing, but also must be made of suitable materials to withstand high winds (e.g., greater than 40 miles per hour). Thus the pole frame structure used to build practice cages typically use rigidly heavy pole frames mainly manufactured out of steel, aluminum, or thick walled plastic tubing. Also, because the pole frames are rigid, the manufacturer must spend a great deal of time and money bending and forming the pole frames into shape.
In some applications, fiberglass tubing has been preferred because plastic tubing becomes brittle in the cold and will crack or break when hit by a moving projectile. However, fiberglass typically cannot be made to have desired strength characteristics. In short, for appropriate sizes, it flexes too much. Also fiberglass poles may split or break. Also, because fiberglass rod is flexible, other rigid materials are used to form corners or angled junctions. Thus fiberglass is typically used to form a frame that is an arch.
The arched fiberglass shape is stronger. However an arch is largest at the bottom of the frame and bends in toward the batter. Thus, the swinging area is reduced for a given foot print. Thus the foot print is enlarged and more material used to make the swinging area equal to a squared frame. Also, since the fiberglass has limited rigidity, the wind has a tendency to blow the arched pole frame side-to-side which overflexes the poles and causes the poles to stress fracture, crack, and/or break.
In U.S. Pat. No. 4,815,736 (Robert Wright), the frame members are formed by a plurality of releasably coupled plastic pipes which are inherently rigid. In U.S. Pat. No. 5,634,638 (Havens, et al.) rounded elbow joints are used to assemble a rigid pole frame. Rigid frames using all rigid frame members are disclosed in U.S. Pat. No. 5,577,721 (Hardee, et al.), U.S. Pat. No. 5,370,385 (Joy), and U.S. Pat. No. 5,820,494 (Gates, et al.).
Flexible frames are also known. See U.S. Pat. No. 5,269,527 (Noval) and U.S. Pat. No. 5,088,740 (Peterson).